Note: Descriptions are shown in the official language in which they were submitted.
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Process for the preparation of hi~hly-branched polyols based on ~lycidol
This invention relates to a process for the preparation of highly-branched
polyols by
polymerisation of glycidol in i:he presence of a hydrogen-active starter
compound with
basic catalysis.
Branched polyols based on gl.ycidol are conventionally prepared by reacting
glycidol
with a hydroxyl-containing compound, for example, glycerol, in the presence of
inorganic (JP-A 61-43627;) ~or organic (JP-A 58-198429) acids as catalysts.
The
polymers thus obtained generally have a low degree of polymerisation. The
polymerisation of glycidol t~o products of higher molecular weight which have
a
narrow molar-mass distribution and complete incorporation of initiators cannot
be
achieved by cationic catalysis, because of the competing cyclisation reactions
(Macromolecules, 27 (1994) 320; Macromol Chem. Phys. 196 (1995) 1963).
Existing
processes using basic catalysis (EP-A 116 978; J. Polym. Sci., 23 4 (1985)
915),
likewise do not lead to colourless products free of by-products and having a
narrow
molar-mass distribution and complete incorporation of initiators. A secondary
reaction
of significance here is in particular the cyclisation as a result of the
autopolymerisation
of glycidol.
Accordingly, the object of the present invention was to find a process for the
preparation of highly-branched polyols based on glycidol whereby the problems
described above are avoided.
Surprisingly, it has now been found that it is possible to prepare colourless,
highly-
branched polyols based on glycidol which are narrowly distributed and have a
defined
structure, if a dilute solution containing glycidol is added to a hydrogen-
active starter
compound, with basic catalysis, the solvent used for the dilution being
continuously
distilled off. In this connection, "defined structure" means that each
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molecule possesses the initiator (hydrogen-active starter compound) as the
core unit
and the degree of polymerisation can be controlled via the monomer/initiator
ratio.
The invention provides a proceas for the preparation of highly-branched
polyols based
on glycidol which have a dei-ined structure, which is characterised in that a
dilute
solution containing glycidol is. added to a hydrogen-active starter compound,
in the
presence of a basic catalyst, the solvent used for the dilution of the monomer
being
continuously distilled off.
As a result of the preferential opening of the epoxide ring at the
unsubstituted end
where basic catalysis is used, a secondary alkoxide is first of all produced,
which,
however, in consequence of the basic catalysis, is in rapid exchange with the
primary
alkoxide. The rapid proton exchange equilibrium ensures that all hydroxyl
groups
present in the system are active as regards polymerisation and that there is a
resulting
development of branching.
Compounds having molecular weights of from I $ to 4,000 and containing from 1
to 20
hydroxyl, thiol and/or amino groups are used as hydrogen-active starter
compounds.
Examples which may be given are: methanol, ethanol, butanol, phenol, ethylene
glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,2-
propylene glycol,
dipropylene glycol, polypropylene glycol, 1,4-butanediol, hexamethylene
glycol,
bisphenol A, trimethylolpropane, glycerol, pentaerythritol, sorbitol, cane
sugar,
degraded st~~rch, water, methylamine, ethylamine, propylamine, butylamine,
stearylamine, aniline, benzylamine, o- and p-toluidine, a,13-naphthylamine,
ammonia,
ethylenediamine, propylenedi,rrnine, 1,4-butylenediamone, 1,2-, 1,3-, 1,4-,
I,5- or 1,6-
hexamethylenediamine, also o-, m- and p-phenylenediamine, 2,4-, 2,6-
tolylenediamine, 2,2'-, 2,4- and 4,4'-diaminodiphenylmethane and
diethylenediamine,
as well as compounds which contain functionalisable starter groups, such as,
for
example, allyl glycerol, 10-undecenylamine, dibenzylamine, allyl alcohol, 10-
undecenol. The starter compound is first of all partially deprotonated by a
suitable
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reagent, for example, by alkali metals or alkaline-earth metals, their
hydrides,
alkoxides, hydroxides or alkyls. Preferably alkali metal hydroxides or
alkoxides or
alkaline-earth metal hydroxides or alkoxides are used, such as, for example,
potassium
hydroxide or methoxide. Any reactive, volatile reaction products (for example,
water,
alcohol) which may form in the course of this are removed (for example, by
distillation). Degrees of deprotonation are generally 0.1% to 90% and
preferably 5% to
20%. In order to avoid problems of intermixture in the course of the reaction,
the basic
initiator system thus prepared is dissolved or dispersed, preferably under
inert gas (for
example, N2, Ar), in an inert solvent I (0.1 to 90 wt.%, based on the quantity
of the end
product) having a boiling point at least S°C above the reaction
temperature. Solvent I
can be an aliphatic, cycloaliphatic or aromatic hydrocarbon (for example,
Decalin,
toluene, xylene) or an ether (for example, glyme, diglyme, triglyme),
preferably
diglyme, as well as mixtures of these. The monomer is added in a solution,
which
generally contains 80 to 0.1 w~t.% and preferably 50 to 1 wt.% glycidol in an
inert
solvent II. Solvent LI can be an aliphatic, cycloaliphatic or aromatic
hydrocarbon (for
example, hexane, cyclohexane, benzene) or an ether (for example, diethyl
ether, THF),
preferably TF~, or a mixture of these, the boiling point being at least
1°C below the
reaction temperature. Solvent II can contain other additives, such as
stabilisers and up
to 10 wt.%, based on the solvent, of other comonomers such as, for example,
propylene oxide, ethylene oxide, butylene oxide, vinyl oxirane, ally glycidyl
ether,
isopropyl glycidyl ether, phenyl glycidyl ether. Solvent II must be a solvent
for
glycidol, but not necessarily for the polyol. The monomer solution is slowly
added to
the mixture of initiator and solvent I, preferably under inert gas (for
example, NZ, Ar).
The feed rate is so chosen as to ensure a good temperature control at the
given reaction
conditions of reaction temperature, glycidol concentration, hydroxyl and
catalyst
concentration. In the course o f the reaction solvent II is continuously
removed from the
reaction mixture by distillation. Here the reaction temperatures are generally
40°C to
180°C, preferably 80°C to 140°C. The reaction is
preferably carried out at normal
pressure or reduced pressure. In the course of the reaction, depending on the
choice of
solvents I and II, the reaction mixture may become inhomogeneous. This does
not
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influence the reaction, however, as long as no precipitation occurs. In order
to work up
the alkaline polymer, in principle all the known techniques for the working up
of
polyether polyols for applications in polyurethane chemistry may be used (H.
R.
Friedel, in Gum, W.F., Riese, W. (Editors): "Reaction Polymers", Hanser
Verlag,
S Munich 1992, page 79). The polyol is worked up preferably by neutralisation.
For this,
the alkaline polymer can first of all be dissolved in a suitable solvent (for
example,
methanol). The neutralisation is preferably carried out by acidification with
dilute
mineral acid (for example, sulfiu-ic acid) with subsequent filtration or
treatment with
adsorbent material (for example, magnesium silicate), particularly preferably
by
filtration through acidic ion-exchange material. This can be followed by a
further
purification by precipitation (for example, from methanol in acetone).
Finally, the
product is freed from traces of solvents under vacuum at temperatures of
20°C to
200°C.
The polymerisation can be carried out in a system of reactors consisting of
three
essential components: a heatable reaction vessel with mechanical stirrer, a
metering
unit and a system for the removal of solvents.
The polyols thus prepared, which are the subject matter of the Application,
have
degrees of polymerisation (based on one active hydrogen atom of the initiator)
of 1 to
300, preferably of 5 to $0. The molar mass of the polyols according to the
invention
can be controlled via the monomer/initiator ratio corresponding to the anionic
process.
The molar mass can be determined, for example, by vapour-pressure osmosis. The
polydispersities are less than 1.7 and preferably less than 1.5. They are
determined by
means of a (CPC calibrated, for example, with polypropylene glycol standards.
The
polyols contain as the core unit the initiator used, which can be detected
preferably by
MALDI-TOF mass spectrometry. The products are preferably colourless, but may
also
be pale yellowish in colour. 'the proportion of branched units in the highly-
branched
polyols, based on all of the ~nonomeric structural units, can be determined
from the
intensity of the signals in the «C-NMR spectrum. The triply substituted carbon
atom
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of the branched units exhibits a resonance between 79.5 ppm and 80.5 ppm
(measured
in d4-methanol, inverse-gated technique). The proportion of the branched units
is equal
to three times the value of this integral value in relation to the sum of the
integrals of
all signals of all units (branched, linear and terminal). The polyols prepared
by the
described process have 10 to 33 mol%, preferably 20 to 33 mol%, branched
units. In
comparison with this, a perfect dendrimer has 50 mol% branched and 50 mol%
terminal units. A linear polyrr~er, on the other hand, has no branched units
and only
linear units anl, depending on the initiator, one to two terminal units. With
20 to 33
mol% branched units, the polyols described can therefore be termed highly-
branched
(see, for example, Acta Polymer., 48 (1997) 30; Acta Polymer., 48 (1997) 298.
The highly-branched polyols thus prepared are versatile highly functional
polymeric
intermediates. The great range of potential initiator molecules and the
carefully
calculated control of the degree of polymerisation (and hence the degree of
functionalisation) opens up diverse possible applications, thus for example,
use as
cross-linking agents and additives in polyurethane formulations, in
biocompatible
polymers, in paints, adhesives and polymer blends, as support materials for
catalysts
and as active ingredients in medicine, biochemistry and synthesis.
In addition, derivatisations carp be earned out through carefully calculated
reactions of
the functional groups.
By means of known per se reactions, the hydroxyl groups can, for example, be
esterified, etherified, aminaled, alkylated, urethanised, halogenated,
sulfonated,
sulfated and oxidised. The tenminal 1,2-diol groups can, for example, be
acetalated or
ketalated or subjected to a diol cleavage.
Double bonds, which are irntroduced into the polyol, for example, via the
starter
compound, can likewise b~e derivatised in suitable form, for example, by
hydroformulation or by radical or electrophilic addition.
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The polyols derivatised in this way in turn open up a multitude of possible
applications, thus, for exarr~ple, use as cross-linking agents and additives
in
polyurethane formulations, in biocompatible polymers, in paints, adhesives and
polymer blends, as support materials for catalysts and as active ingredients
in
medicine, biochemistry and s~mthesis, as reaction compartments for the
catalysis and
production of nanoparticles.
The highly-branched polyols prepared according to the invention can also be
reacted
with a second epoxide mononner {and optionally further epoxide monomers) such
as,
for example, propylene oxide, ethylene oxide, butylene oxide, vinyl oxirane,
glycidol,
ally glycidyl ether, to form block copolymers. Preferably ethylene oxide,
propylene
oxide, butylene oxide, vinyl oxirane and mixtures thereof are used. Preferably
the
highly-branched polyol is reacted, using basic catalysis, without intermediate
working
up and in the same reaction vessel, with the epoxide monomer/mixture of
epoxide
monomers, optionally with the addition of a solvent. A further deprotonation
of the
highly-branched polyol by means of the basic reagents described above may also
take
place. Degrees of deprotonation are generally 0.1% to 90% and preferably 5% to
20%,
based on one OH group. The reaction temperatures here are between -40°C
and 200°C,
preferably between 20°C and 180°C, particularly preferably
between 60°C and 160°C.
The reaction can be earned out at total pressures of between 0.001 and 20 bar.
The
block copolymers are worked up preferably by means of the techniques already
described above for working up polyether polyols.
The block copolymers thus produced have degrees of polymerisation (based on
one
OH group of the highly-branched polyol used) of 1 to 70, preferably 1 to 10.
The
molar mass can be controlled via the monomer/initiator ratio corresponding to
the
anionic process. The molar mass can be determined, for example, by vapour-
pressure
osmosis. The polydispersitie s are less than 2.0 and preferably less than 1.5.
They are
determined by means of a <~P'C' calibrated, for example, with polypropylene
glycol
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standards. The products are mainly colourless oils, which may also have a pale
yellow
colouring. The polymers have OH values (mg KOH equivalents per g polymer)
between 750 and 14, preferably between 400 and 30.
The highly-branched block copolymers thus produced are versatile highly
functional
polymeric intermediates. The great range of block-copolymer compositions opens
up
diverse possible applications, thus for example, use as cross-linking agents
and
additives in polyurethane formulations, in biocompatible polymers, in paints,
adhesives and polymer blends, as support materials for catalysts and as active
ingredients in medicine, biochemistry and synthesis, as reaction comparhnents
for the
catalysis and production of nanoparticles, a reaction compartment in this
connection
meaning a spatially limited reaction space in the nanometric range.
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Examples
Examine 1 (Trimethylolpropane as initiator)
1.2 g trimethylolpropane was melted in a 250 ml glass reactor heated to
100°C and
reacted with 0.7 ml potassimm methoxide solution (25% in methanol) and excess
methanol was then removed under vacuum. The residue was dissolved in 15 ml dry
diglyme under an inert gas (t~~r). Then, at 140°C, a solution of 34 g
freshly distilled
glycidol in 100 ml dry THF was added at a rate of 5 ml per hour to the
reaction
mixture, THF' being continuously distilled off. On conclusion of the addition,
the
reaction mixture was dissolved in 150 ml methanol and neutralised by
filtration
through an acidic ion-exchange resin (Amberlite~ IR-120). The filtrate was
precipitated out in 1600 ml acetone and the polymer obtained was dried for 12
hours at
80°C under vacuum. 33 g of a colourless, highly viscous liquid having a
molar mass of
3,700 (degree of polymerisation 16 per active hydrogen) and a polydispersity
of 1.15
was obtained. All molecules contained the initiator as the core unit and had
26%
branched structural units.
Example 2 (Polyethylene glycol 600 as initiator)
As in the procedure described in Example 1, 6.0 g polyethylene glycol having a
molar
mass of 600 was reacted with 0.25 ml potassium methoxide solution (25% in
methanol) at 100°C, excess methanol was removed under vacuum and the
residue was
dissolved in 10 ml dry diglynne. At a bath temperature of 140°C, 14 g
glycidol in 100
ml dry THF was added at a rate of 5 ml per hour. The polymer was isolated as
in
Example 1. 19 g of a colourless, highly viscous liquid having a molar mass of
2,000
(degree of polymerisation 9.:> per active hydrogen) and a polydispersity of
1.13 was
obtained. All molecules contained the initiator as the core unit and had 26%
branched
structural units.
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Example 3 (Stearylamine as initiator)
2.1 g stearylarnine was melted in a 250 ml glass reactor heated to
100°C and reacted
with 1.2 g glycidol. Then 0.9 ml potassium methoxide solution (25% in
methanol) was
added and excess methanol ways removed under vacuum. The residue was dissolved
in
ml dry diglyme at 140°C. 55 g glycidol in 100 ml dry THF was added at a
rate of 5
ml per hour. T'he polymer was isolated by a procedure similar to that in
Example 1. 54
g of a colourless, highly viscous liquid having a molar mass of 7,200 (degree
of
polymerisation 47 per active hydrogen of the amine) and a polydispersity of
1.23 was
10 obtained. All molecules contained the initiator as the core unit and had
27% branched
structural units.
Comparison Example 4 (Procedure without solvents, similar to EP-A 116 978)
15 Under the conditions and wil:h the educts from Example 2, the
polymerisation was
carried out in the absence of any solvents and glycidol was added dropwise to
the
reaction mixture. 19 g of a yellowish, highly viscous liquid having a molar
mass of
1,600 (degree of polymerisation 7 per active hydrogen) and a polydispersity of
1.84
was obtained. Only 50% of all molecules contained the initiator as the core
unit.
Example 5 Production of block copolymer
In a 250 ml glass reactor heated to 100°C, 1.0 g of a highly-branched
polyol based on
glycidol, prepared by the process described in Example 1 and having a molar
mass of
4,000 (corresponding to 52 OH terminal groups), was reacted with 0.1
equivalents of
potassium hydride per active hydrogen atom. SO ml propylene oxide was added in
such
a way that the internal temperature was maintained between 80°C and
95°C. On
conclusion of the addition, the reaction mixture was dissolved in 150 ml
methanol and
neutralised by filtration through an acidic ion-exchange resin (Amberlite~ IR-
120).
The filtrate was freed from methanol and dried for 12 hours at 80°C
under vacuum. 42
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g of a colourless, highly viscous liquid having a molar mass of 12,300, a
polydispersity
of 1.3 and an OH value of 234 mg KOH/g was obtained.
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